Such a clutch plate is generally formed from a metallic support plate which includes axially deformable portions that constitute a progressive action device, with two ring-shaped friction pads being carried on either side of the support plate. The purpose of the progressive action device is firstly to enable progressive transmission to be received without snatching of the engine torque during an operation of engaging the clutch, and secondly to compensate for geometrical variations in the surface of the clutch.
The friction liners are usually attached to the support plate by riveting. This results in limitation of the useful thickness of each friction liner to that part which lies outside the level of the heads of the securing rivets. For this reason, the weight of the clutch plate is detrimentally increased, and in particular, its inertia is increased. This gives rise to difficulty in achieving synchronism during declutching and gear changing operations.
In order to avoid having to secure the friction pads by riveting, it has already been proposed to attach them adhesively on to flat metallic plates. Resilient arms, made of elastomeric material, are interposed in discrete zones. Such an arrangement is for example described in the specification of United States Pat. No. 2 253 316 and that of French Pat. No. 2 450 977.
In another type of construction, which is described in the specification of published European patent application No. EP 0 252 583A, the friction pads are secured on a flat metallic support plate through circular, concentric beads or bands of elastomeric material.
In these known expedients, the arms or bands of elastomeric material do however have the disadvantage that the elastomer is distributed unevenly. This gives rise to nonuniformity in the deformation of the progressive action device in the region of the friction pads, and also gives rise to premature wear of the latter because the heating which occurs in service is concentrated in zones having somewhat limited local zones of the friction pads.
An elastomeric material such as that used in the present state of the art as described above deforms by a flow action, provided that in all the zones concerned there is sufficient space to enable this to take place. This is in general not the case in known clutch plates.